The present invention relates to an improved system for automatically positioning a platform-type work station on a drilling device, such as a drill rig.
One class of prior art drilling devices employs a transfer arm which is pivoted about a horizontal axis to raise and lower drilling tubulars, such as drill pipe, between a horizontal position near ground level and a vertical position aligned with the drilling axis of the drilling device. Such transfer arms can materially increase the working efficiency of drill rigs in that they simplify and speed the raising of drill pipe from a storage position at or near ground level to a raised position in alignment with the drill string, as well as the removal of pipe from the drill string to the storage position.
In the past, one commercially developed form of such drilling devices used a working platform which was near ground level. In this prior art device, no working platform was positioned in the region between the transfer arm and the drill string in order to allow the transfer arm to approach the drill string closely when in the raised position. With such prior art devices, the absence of a working platform in the region between the transfer arm and the drill string did not create a significant problem, because a worker could simply stand on the transfer arm when in the lowered position in order to walk from one side to the other of the working platform.
Recently, the working platform on some such drilling devices has been raised some distance above the ground in order to allow suitable safety equipment to be placed around the drill string above the ground but below the working platform. In one such device, the working platform is raised ten feet above ground level. In such an arrangement, the absence of a working platform between the drill string and the transfer arm can create serious inconveniences, due to the fact that it is no longer possible simply to walk on the transfer arm in order to move from one side to the other of the working platform. Thus, a need exists for an improved arrangement which provides a working platform in the region between the drill string and the transfer arm, yet which still allows a transfer arm to move to the vertical position, without coming into contact with the platform.